Fine-needle aspiration of the thyroid: Rate and causes of cytohistopathologic discordance

Fine-needle aspiration (FNA) of the thyroid gland is a widely utilized, sen sitive, specific, and cost-effective method for the evaluation of thyroid n odules. The purpose of this this study was to evaluate the accuracy of thyr oid FNA and causes of cytohistological discordance in our institution. Six hundred twenty-five thyroid FNAs obtained from 503 females (mean age, 54) a nd 122 males (mean age, 51) in whom histopathologic follow-up material was available for review, were analyzed. FNAs were classified as: nondiagnostic , negative, intermediate, and positive for malignancy and the histopatholog ic material was categorized as benign or malignant The review revealed 93% sensitivity and 96% specificity for the FNA diagnoses. The FNA results were diagnostic in 87%, indeterminate in 6%, and nondiagnostic in 7% of the cas es. Cytohistologic correlation was achieved in 88% of the cases. The false- negative rate was 4% and the false-positive rate was 8%. The most common pi tfalls for false-negative diagnoses consisted of suboptimal material and un derdiagnosis of papillary carcinoma due to cystic degeneration. The most co mmon pitfall for false-positive cases was overdiagnosis of follicular neopl asms. Our study confirmed that FNA of thyroid nodules can be performed with high sensitivity and specificity by experienced clinicians or pathologists . The application of strict specimen adequacy rules for FNA interpretation is likely to decrease the rate of false-negative and false-positive diagnos es. (C) 2000 Wiley-Liss, Inc.